Automatic lens system assembly operations are known. They do not require a large number of human personnel assembling lens elements into a lens barrel. Thus, an automatic lens system assembly operation can provide significant cost savings when a large number of lens systems are being assembled. An automatic lens system assembly operation may use, for example, a robotic arm that picks up (by suction, claw or otherwise) lens elements from a lens holder (such as a lens tray), and assembles them into the lens barrel. In this type of assembly it is important and often critical to know a precise location and orientation of each lens element, so that the robotic arm can pick up the lens element from the lens tray. If a lens element shifts and changes its position on the lens tray, and if the lens element is being picked up by suction, the amount of suction may not be enough to successfully pick up the lens element. Similarly, if the claw of the robotic arm can not successfully grab the lens element, the robotic arm may not be able to successfully remove the lens element from the lens tray.
It is known that the performance of a lens system may be improved if one or more lens elements in a lens system have coated surfaces. There are many lens coating methods. All of them require that lens elements be held in place during a coating operation. The lens elements are usually: (1) brought into a coating laboratory in a lens tray (such as those described below), (2) taken out of the lens tray, (3) loaded into a lens coating tray, (4) coated with a required coating material, (5) taken out of the lens coating tray, (6) loaded back into the lens tray and transported into an assembly area. At this point the lens elements may be taken out from the lens tray and loaded into a special tray that holds lens elements in a precise predetermined location for their subsequent use in the automatic assembly.
As stated above, lens trays for holding lens elements during transportation and storage are known. For example, steel lens trays are used that have a plurality of long, narrow grooves machined into them. Each of the grooves can hold a plurality of lens elements adjacent to one another (see FIGS. 1A, 1B). The lens elements are placed into these lens trays by holding the lens trays in either a vertical position or in a tilted position with the openside pointing upwards. If needed, the lens elements can be transported to a coating lab where the lens trays are placed in a horizontal position. The lens elements may be coated while still in the lens trays. Afterwards, the lens trays are shipped to the assembly area. The lens elements are removed from the lens tray by holding the lens tray in a tilted position with the open side pointing downwards, so that the lens element can slide out of the lens tray. A plurality of chutes then guide the lens elements towards the lens barrels into which they are assembled. The surfaces of the grooves are machined, and the lens elements do not slide out of the lens trays at a constant speed. This causes bunching of the lens element and clogging of lens chutes, interfering with the efficient automatic lens assembly. In addition, steel lens trays are heavy and are expensive to manufacture. When the lens trays of this configuration are injection molded, the grooves assume a bow like shape and the lens elements again do not slide out at a constant speed and tend to bunch together and, in addition, do not consistently hold the lens elements in.
U.S. Pat. No. 4,494,667 discloses a wire rack lens tray that keeps lens elements from contacting with foreign surfaces that may scratch an optical surface of a lens element. These trays can be stacked on top of one another for efficient storage. However, the disclosed trays are not suitable for holding lens elements during a surface coating operation (such as vapor deposition) because the wire support structure 2 of the lens tray covers parts of lens elements' optical surfaces 3 (see FIG. 1C). Thus the lens elements would have to be taken out of the disclosed tray and put into another support structure during the coating operation. After the lens elements are coated they can be placed back into the wire rack lens tray. Finally, the disclosed lens trays are not suitable for use in an automatic lens assembly that requires the exact knowledge of lens elements' center coordinates. This is because the lens elements supported by this lens tray are supported only on one side (i.e., back side as shown in FIG. 1D), the lens elements can slide in the direction shown by arrow 5.
Japanese laid open patent application JP 8122604-A discloses a lens tray for horizontally supporting lens elements of different diameters. This lens tray includes "a set of loading holes having circular conic shape smoothly reducing in diameter in depth direction." Because this conic shape provide gradual reduction in diameter, it can accommodate lens elements of different diameters. However, because there is no radial constraint on the location of a lens element within a hole, a lens element can move within this hole. Thus, the disclosed lens tray can not be used during a mechanized assembly that requires the exact knowledge of lens center coordinates.
U.S. Pat. No. 4,084,700 discloses a display rack for displaying lens elements. The disclosed rack has a body panel with a plurality of tabs for vertically supporting the lens elements. However, the disclosed display rack is not suitable for holding lens elements during a surface coating operation, such as vapor deposition, because the lens elements are held vertically and because the tabs cover parts of lens element's front surfaces. In addition, the solid wall of the body panel does not provide an access to the rear surfaces of the lens elements. Thus, if the rear lens surfaces need to be coated, the lens elements will need to be taken out of the display rack and flipped around. Finally, the lens elements are not in the right orientation for their assembly within a lens barrel, if such assembly is required. Because the lens elements are supported vertically on the body panel, rather than horizontally, they would have to be rotated (by about 90 degrees) prior to their placement within a vertical lens barrel.
U.S. Pat. Nos. 4,796,756, 3,889,815 and 5,584,400 also disclose optical lens trays. The disclosed trays also cannot be used to support lens elements during a coating operation because the lens elements are located behind one another and thus block one another. In addition, the lens elements are not in the right orientation for their assembly within a lens barrel, if such assembly is required. Because the lens elements are stacked vertically within the lens tray, rather than horizontally, they would have to be rotated (preferably by 90 degrees) prior to their placement within a lens barrel.
Finally, many different polymer materials exist. Their outgassing characteristics are known. For example, in the NASA publication SP-105 entitled "Vacuum Technology and Space Simulation", pg. 219 discloses the table of outgassing values for different materials. It is noted that if the outgassing measurement test was performed under different conditions the outgassing values can change, but the relative position of the materials on the list would remain the same.